The invention is directed to a device for monitoring the needle thread in a sewing machine.
Devices of said type are known and serve to monitor yarn breakage during sewing. They detect if the needle thread has been correctly threaded in the sewing machine, in particular in automatic threading devices.
From the GDR-publication 83897 a device for monitoring the needle thread is known, in which the needle thread running from the thread tension device to the thread lever is deflected at a regulator spring. A cam switch is connected to the regulator spring, which in case of changing thread tensions glides through a light bar and in case of an insufficient tension, e.g., caused by yarn breakage, triggers a signal. In this known device, in case of detection, there is only the possibility to detect yarn breakage or, to a limited extent, excess change of thread tension. No other detailed data regarding the functions of the sewing machine can be detected.